alkanes - mwitteppode/5_alkane.pdf · 2 sorachai saelim physical properties of alkanes and...

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AlkanesAlkanes

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Physical Properties of Alkanes and Cycloalkanes

Boiling points of unbranched alkanes increase smoothly with Boiling points of unbranched alkanes increase smoothly with number of carbons

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Constitutional isomers have different physical properties (melting point, boiling point, densities etc.)

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จงเรียงลําดับจดุเดือดของสารตอไปนี้จากมากไปหานอย

3,3-dimethylpentane, n-heptane, 2-methylheptane,

t 2 th lhn-pentane, 2-methylhexane

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Synthesis of Alkanes and Cycloalkanes

H d ti f Alk d Alk-Hydrogenation of Alkenes and Alkynes

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ี่ G h S l d C i F hl O i Ch i t ed(ทีมา: Graham Solomon and Craig Fryhle, Organic Chemistry, 7ed)

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Reduction of Alkyl Halides

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-Radical Reactions

Production of Radicals-Homolysis of relatively weak bonds such as O-O or X-X bonds can occur with addition of energy in the form of heat or light

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The relative stabilities of radicals follows the same trend as for carbocations

-The most substituted radical is most stable

R di l l d fi i b i -Radicals are electron deficient, as are carbocations, and are therefore also stabilized by hyperconjugation

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The entire mechanism is shown below

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Br2 , light

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Br2 , light

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l i i f i d hl iSelectivity of Bromine and Chlorine

Bromine is much less reactive but more selective than chlorine in radical halogenation

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Combustion reaction

CnH2n+2 + O2 CO2 + H2O

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